This application relates generally to seismic data acquisition and processing, and more specifically to systems and methods for processing seismic data. In particular, the application encompasses full waveform inversion (FWI) techniques adapted to derive high-fidelity models of subsurface structures, including petrochemical reservoirs and other geophysical features.
Petrochemical products are ubiquitous in the modern economy, and can be found in everything from oil and gasoline to medical devices, children's toys, and a wide range of everyday household items. To meet the continuing demand for these products, oil and gas reserves must be accurately located and surveyed, so that these important resources can be effectively managed. As a result, there is an ongoing need for new seismic sensor systems, and for more advanced seismic exploration and imaging technologies.
Scientists and engineers typically utilize seismic wave-based exploration to locate new oil and gas reservoirs, and to survey and manage existing reserves over time. Seismic surveys are performed by deploying an array of seismic sensors or receivers over the region of interest, and monitoring the response to controlled emission of seismic energy via one or more seismic sources such as vibrators, air gun arrays, and explosive detonations. The response depends upon the seismic energy reflected from mineral reservoirs and other subsurface formations, allowing an image of the corresponding geological structures to be generated.
Conventional marine seismic surveys typically proceed by towing an array of seismic sensors or receivers behind a survey vessel, with the receivers distributed along one or more streamer cables. A set of air guns or other seismic sources is used to generate the seismic energy, which propagates down through the water column to penetrate the ocean floor (or other bottom surface). A portion of the seismic energy is reflected from subsurface structures, and returns through the water column to be detected in the streamer array. Alternatively, the seismic receivers can also be disposed along an ocean-bottom cable, or provided in the form of autonomous seismic nodes distributed on the seabed.
Geophysical data pertaining to subsurface structures is acquired by observing the reflected seismic energy with an array of seismic receiver components. Suitable seismic receivers include pressure sensors and particle motion detectors, which can either be provided individually or combined together in close proximity within a receiver module or seismic node. Suitable pressure sensors include hydrophones and hydrophone arrays adapted to record pressure measurements of the seismic wavefield propagating through the surrounding water column, or other seismic medium. Suitable particle motion sensors include accelerometers and geophones configured to provide single-axis or multi-axis (three-dimensional) velocity measurements, in order to characterize motion of the seismic medium in response to propagating seismic waves.
Seismic signals from the receiver arrays can be processed to reconstruct the seismic wavefield, and to generate images of the subsurface geology. The seismic images can also characterize subsurface composition, and geophysical structures in and around the survey area. The image quality depends on the fidelity of the wavefield reconstruction and other signal processing capabilities, creating a substantial ongoing demand for more advanced methods of inversion-based seismic imaging.